What makes a song a song of summer: First, timeliness (any time between the months of April and July). Anthemic drumbeat (something in the classic 4/4, not waltzy, a lot of bass drum). Some oh-oh-oh's. A lot of repetition. A syncopated opening riff doesn't hurt. Neither does Rihanna. Nor does hitting the chorus at or before the 1:30 mark. This summer, Passion Pit has done most of these things, mostly ditching the band's incredibly high falsetto for a more mature, deeper vocal sound — making their danceable tunes that much more listenable. The just released "Take a Walk" is — at least we're calling it right now — a song of summer. Which is worth something, even if it doesn't come with Rihanna.